A US woman who shot and killed her husband and two adult children before taking her own life is thought to have committed the shocking crime as a result of being ostracised from the religion she was raised in.

A federal judge sentenced a former Arkansas judge Wednesday to five years in prison — a stiffer punishment than prosecutors recommended — after he admitted giving young male defendants lighter sentences in return for personal benefits that included sexual favours.

Every time I tell a mate I’m doing a story on cryptocurrency, they invariably ask me the same two questions: should they invest their own hard-earned money, and which cryptocurrency will get them a Lamborghini/yacht/island quickest?

In a 60 Minutes online exclusive, reporter Liz Hayes quizzed Australian Prime Minister Malcolm Turnbull on his relationship with the unpredictable Twitter aficionado and US president Donald Trump ahead of their meeting at the White House Friday.

Tough new laws announced for G20 safety

Kites will be outlawed in inner-city Brisbane next year as part of a raft of new laws to be introduced during the G20 summit.

Police minister Jack Dempsey says the new legislation, yet to be introduced to parliament, will help ensure the safety of world leaders when they converge on Queensland's capital in November next year.

Mr Dempsey and senior police were reluctant on Tuesday to go into detail about the legislation.

But the police minister said it would include increased police arrest powers, the ability to detain suspicious people and restrictions on various items, including air-borne items such as kites, for the duration of the event.

"There's a lot of air things that can be used to disturb a particular event," Mr Dempsey told reporters.

"We're looking at a broad spectrum of what's happened in the past and the potential to fit in with this particular site here."

Queensland Police Assistant Commissioner Katarina Carroll said her officers were also liaising with those from previous host cities to help deal with professional protesters like those who rioted in Toronto in 2010.